A Level H2 Biology Evolution Diversity Quiz

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A-Level Biology H2 Quiz - Evolution Diversity

Name: ____________________
Class: ____________________
Date: ____________________
Score: ________ / 65

Duration: 90 Minutes
Total Marks: 65
Instructions: Answer all questions. Use the space provided. Write clearly and use precise biological terminology.

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Section A: Foundations of Evolution (Questions 1–7)

1. Define the term natural selection and state the three necessary conditions for it to occur within a population. [3]
   
   
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2. Distinguish between homologous structures and analogous structures. Provide one example of each. [4]
   
   
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3. Explain why a high mutation rate in a viral population, such as HIV, increases the likelihood of the virus developing resistance to antiretroviral drugs. [3]
   
   
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4. Describe the role of genetic drift in small, isolated populations. How does this differ from natural selection? [4]
   
   
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5. Explain the concept of adaptive radiation using the example of Darwin's finches. [4]
   
   
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6. Compare and contrast divergent evolution and convergent evolution. [4]
   
   
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7. State the difference between gradualism and punctuated equilibrium in the fossil record. [3]
   
   
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Section B: Speciation and Diversity (Questions 8–14)

8. Describe the process of allopatric speciation. Use a specific example to illustrate your answer. [5]
   
   
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9. Explain how sympatric speciation can occur without geographic isolation. Mention at least one mechanism (e.g., polyploidy or behavioral isolation). [4]
   
   
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10. Define reproductive isolation and distinguish between pre-zygotic and post-zygotic isolating mechanisms. [4]
    
    
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11. A population of birds develops different mating calls based on the forest density they inhabit. Explain how this leads to speciation. [3]
    
    
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12. Explain why the biological species concept is difficult to apply to asexual organisms or fossils. [3]
    
    
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13. Discuss the impact of founder effect on the genetic diversity of a new colony. [3]
    
    
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14. Describe how sexual selection can lead to the evolution of traits that may seem disadvantageous for survival. [4]
    
    
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Section C: Molecular Evidence and Classification (Questions 15–20)

15. Explain why comparing the amino acid sequence of cytochrome c is a more reliable indicator of evolutionary relationship than comparing overall morphology. [4]
    
    
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16. With reference to a hypothetical DNA sequence, explain how the number of base pair substitutions is used to estimate the time since two species diverged from a common ancestor. [4]
    
    
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17. Define a cladogram and explain how a "node" represents an evolutionary event. [3]
    
    
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18. Explain the difference between monophyletic and paraphyletic groups in phylogenetic classification. [4]
    
    
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19. Discuss the advantages of using rRNA (ribosomal RNA) sequences for classifying organisms across different domains (Archaea, Bacteria, Eukarya). [4]
    
    
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20. Explain how the use of molecular clocks can be calibrated using fossil evidence. [4]
    
    
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Answer Key - A-Level Biology H2 Quiz: Evolution Diversity

Section A: Foundations of Evolution

1. Definition: The process where organisms better adapted to their environment tend to survive and produce more offspring. Conditions: (1) Variation in traits, (2) Heritability of traits, (3) Selection pressure/differential survival. [3]
2. Homologous: Similar anatomy due to common ancestry but may have different functions (e.g., pentadactyl limb in humans and whales). Analogous: Similar function but different evolutionary origin due to convergent evolution (e.g., wings of insects and wings of birds). [4]
3. High mutation rate $\rightarrow$ creates high genetic variation in the viral population. Some mutations may randomly confer resistance to the drug. Under the selection pressure of the drug, resistant strains survive and replicate, leading to a population of resistant viruses. [3]
4. Genetic Drift: Random change in allele frequencies, especially in small populations (e.g., bottleneck). Difference: Drift is stochastic/random; Natural Selection is non-random and based on fitness/adaptation. [4]
5. Adaptive Radiation: Rapid evolution of diversely adapted species from a common ancestor. Example: Finches arrived at Galapagos $\rightarrow$ occupied different niches (seeds, insects, nectar) $\rightarrow$ selection for different beak shapes $\rightarrow$ speciation. [4]
6. Divergent: Related species evolve different traits due to different environments (leads to homology). Convergent: Unrelated species evolve similar traits due to similar selection pressures (leads to analogy). [4]
7. Gradualism: Evolution occurs at a slow, steady rate over long periods. Punctuated Equilibrium: Long periods of stasis interrupted by brief periods of rapid evolutionary change. [3]

Section B: Speciation and Diversity

8. Process: Geographic isolation $\rightarrow$ prevention of gene flow $\rightarrow$ different selection pressures/mutations in separate populations $\rightarrow$ accumulation of genetic differences $\rightarrow$ reproductive isolation. Example: Darwin's finches or squirrels separated by the Grand Canyon. [5]
9. Sympatric: Speciation within the same geographic area. Mechanism: Polyploidy (common in plants) creates instant reproductive isolation; or behavioral isolation (different mating seasons/preferences). [4]
10. Reproductive Isolation: Biological barriers that prevent members of two species from producing fertile offspring. Pre-zygotic: Occurs before fertilization (e.g., temporal, behavioral). Post-zygotic: Occurs after fertilization (e.g., hybrid sterility/inviability). [4]
11. Different calls $\rightarrow$ females only respond to specific calls $\rightarrow$ non-random mating $\rightarrow$ reduction in gene flow between groups $\rightarrow$ genetic divergence $\rightarrow$ speciation. [3]
12. Biological species concept relies on the ability to interbreed and produce fertile offspring. Asexual organisms do not interbreed; fossils cannot be bred. [3]
13. A small group starts a new population $\rightarrow$ only a fraction of the original gene pool is present $\rightarrow$ reduced genetic diversity $\rightarrow$ increased risk of inbreeding or fixation of deleterious alleles. [3]
14. Traits (e.g., peacock's tail) are selected because they indicate fitness to mates $\rightarrow$ increased mating success outweighs the cost of predation risk or energy expenditure. [4]

Section C: Molecular Evidence and Classification

15. Morphology can be misleading due to convergent evolution (analogous structures). Cytochrome c is a highly conserved protein; differences in amino acid sequences reflect mutations accumulated since divergence, providing a direct molecular record of ancestry. [4]
16. Assume a constant mutation rate (molecular clock). Count differences in base pairs between two species. The greater the number of substitutions, the longer the time since they shared a common ancestor. [4]
17. Cladogram: A branching diagram showing the evolutionary relationship between species. Node: Represents the most recent common ancestor of the lineages branching from it. [3]
18. Monophyletic: Includes the common ancestor and all its descendants. Paraphyletic: Includes the common ancestor but excludes one or more descendant groups. [4]
19. rRNA is present in all living organisms (universal). It performs a critical function (protein synthesis), so it evolves very slowly. This allows for the comparison of very distantly related taxa (e.g., Bacteria vs Archaea). [4]
20. Use fossils to determine the absolute date of a known divergence event (e.g., 50 million years ago). Calculate the number of mutations between those two groups. This establishes the "rate" of mutation per million years, which can then be applied to other sequences. [4]